Transmitter



Aug, 13, 1929. w D, PACK 1,724,360

` TRANSMITTER Filed April 19, 1928 @lulu mnmunl Y I william Y Patented Aug. 13, 1929.

UNITED STATES' WEHBLI D. PACK, F CHICAGO, ILLINOIS.

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applicati@ med pra 19,

This invention relates to improvements in transmitters, and is here shownembodied 1n a device particularly adapted for transmitting the 'impression on .a phonographic record to a distant point by electrical impulses.

'Such a device is frequently referred to as a magnetic pickup for phonograph records,

, and is used to transmit the impression to a radio-receiving s'et in a well known manner so that the sound recorded will be heard from the phones or loudspeaker of the radio set.

Although I have here shown the invention embodied in the articular kind of device referred to above, 1t is to be understood that it may have many other uses. The invention broadly contemplates a device for transformmg mechanical into electrical energy and vice` versa, and may be used in a great varietyof ways. For exam le, with the necessary changes and modi cations,'it may be embodied in microphones, loudspeakers, electrical measuring devices, and the like.A

. One of the features of my invention 1s 2 5 the provision of a magnet having a single and a double pole; or single and double pole pieces, both lying in the magnetic flux cir- N Y, ,Cuit Hereafter, when I use the'term pole piece I mean also to include pole, since there does not necessarily have to be a'sepaf` rate pole piece in eachcase. That is, for example, one pole of the magnet could be divided instead of providing a separate divided pole piece therefor. I find itv adi' visable, however, to provide aA separate divided pole piece in order to make the same of relatively soft iron. Means are provided for vibrating one of the pole pieces, relatively to the other, in response to the vibrations or waves to be transmitted. Such vibrations of one of the pole pieces changes the relative roportions of the magnetic flux flowing tl-hroughthe two parts of the double ole piece. A' coil is provided for conducting the currentsgenerated by such changesin flow. It is obvious thatsuch curvrents will corres nd to the movements of the vibrating po epieces. It will be seen that, although the relative proportions of iow through the two parts of the double pole piece are varied, the total iiow through the entire circuit will be substantially constant. This is of particular advantage since, in such a device, it is not necessary to change or vary the ow through the magnet itself which is 192s. serial' No. 271,199.

ordinarily made of relatively harder iron. The double pole ,piece where the variations in flow occur is preferably jof relatively soft iron, thus reducing lag to aminimum and reatly increasing the sensitivity of the evlce.- v

In that form of device embodying my i11- vention shown in the accompanying drawings, Figure 1 is a view in perspective, Fig. 2 is aview in side elevation showing the cover 1n section,-Fig. 3.-'is an enlarged view taken on the line 3 of Fig. 2; Fig. 4 is a view taken on the line 4 of Fig. 2,-' Fig. 5'is a diagrammatic view of thewiring, and Fig. 6 is a view taken on the line 6-6 of Fig. 3'.' V

As shown in the drawings,l10 indicates'a phonographic'record on the turntable 11.

My improved transmitter com risesa natural horseshoefmagnet 12 wit one Vpole slightly longer than the other and bent inwardly slightly. For convenience, I have f given the poles the usual designationsS and N, the latter being longer. i

The shorter pole-S 4carries an inverted U shaped member comprising the cross-bar '13v with the two depending arms 13%. Each of these arms is equipped with an inwardly projecting core '14 with its outer end threaded into the arm, as indicated by 14, in'order to afford adjustability. The cross-bar 13 with the arms 13a and cores 14 may be considered a bifurcated or divided pole piece' for the pole S. Carried on the inside of each arm 13a and ,surrounding the core 14 is a coil of wire 15, preferablycarried on a suitable spool 15. The spool may be attached to the arm by cementing. y

The longerf'pole N of the magnet carries a rockable armature or pole-piece inthe form `of' a flattened bar l16 with its inner' end lying between the ends of the cores 14, 14, and its outer end 16a projecting through the e11- larged hole,I N in the pol'e N. The outerend' of the armature 16 is provided with a square cross-bar 17 lying on one edge in a groove 18 in the pole N. .The angle of the sides of the groove 18 is somewhat greater than the angle of the adjacent sides of the cross-bar 17 so that such cross-bar is permitted to rock on the edge 17a which lies in such groove'. The cross-bar 17 is held in the groove 18 by a cover plate 19 attached to the pole N by the screws 20. 21, 21, indicate strips yof rubber or similar material placed between the cross-bar 17 and 'the cover plate 19 to permit 110 Y' rocking of the cross-bar 17 to vibrate the armature 16 between The cross-bar 17 is provided with adepending needle carrying. arm 22 alined with the armature 16. 'The arm 22 is preferably One end of such cross-bar is 'provided' with an intersecting thread hole to receive'the needle holding screw 24. By means of this of theneedle 23, caused by its relative travel' construction, vibrations of the pointed end in the groove on the record, will cause rocking of the cross-bar 17 on its edge 17"`lying in the groove 18, and corresponding vibration of the armature 16 between the ends of the cores 14.

In Fig. 5, I have shown diagrammatically the windings of the coils 15. It will be seen:

that they are both wound inthe same direc-v tion, the inner terminals being connected as indicated b 15. The two outer terminals .as indicate by. 1'5" n. are attached to a suitable insulating block 25 carried by the mem'- ber 13. The block 25 is equipped with suitable binding posts 26 to permitatta'chment of the connecting wires27 to maintain the same in electrical connection with the ter. .minals 15".

28 indicates a suitablehousing or cover which may be provided with connecting devices 29 to receive the lead wires 30 on the outside and-the connecting wires 27 on the inside and'maintain the same in electrical connection. Thelead wires 30 may be conducted to. any device (not shown), which4 is adapted to receive electrical impulses which will be generated by the vibrations of the armature 16. A

It will be seen that the armature or polepiece 16 will take the polarity of the N pole and the cores 14 on the other pole-piece will bot-h take the polarity of the S pole. This isv clearly shown in the diagrammatic view' in Fig. 5. Vibration of the needle 23 will vibrate the armature or pole-piece 16 be# tween .the two cores 14, 14. Such' vibrationA will change the relative proportions of mag-Q netic flux owing through the two coresy 14,- 14, and consequently generate currents in the coils in accordance .with such changes. i

It is to be noted, however, that the amount of fiux flowing through the entire circuit is' -not substantially changed. In- Fig. 5, the. arrows on the cores -14 indicate diagram-` matically the owof magnetic iiux from the the ends' of the cores' N armature through both of the cores 14 tothe S pole ofthe magnet. Whenthe armature is midway between the cores 14 the 'iiow will be in substantially equal amounts through the twol cores. When the .armature moves nearer to one,of the cores :(for example, to drilled outto receive a needle, the socket extending upwardly through the cross-bar 17 other. This change'in the relative proportions `of flow through the two cores will causejfaelectrical current to' be generated through the coils 15 in the direction indi` cated by the arrows.- In llike manner each movement or vibration of the. armature 16 between the cores 14, 14, will change the path of part of the flow. of magnetic "flux and generate a corresponding current in the coils 15. 'While I have shown and described certain embodimentsof my invention, it is to .be

understood that it iscapableo many lmodiiications. Changes, therefore, l.in thefconstruction and arrangement may vbe` madeA without departing from the spirit and scope of the invention as disclosed in the appendedclaims, in which it is my intention to claim all" novelty inherent in my invention asv 2' broadly as possible in view of the prior art..

-VVhat I claim as new, and desire to secure by Letters Patent, is: y

' In a transmitting `device of the character described; a magnet; a transversely arranged U-Shaped coil supporting member carried by one pole ofthe magnet; la pair of trans- .versely arrangdLlg-,alined coils carried by the arms of said coilsup' orting memberycores in said coils with t eir inner ends {separated; an armature having a cross-piece with a sharp edgefand pivotally supported by the other pole 'of the magnet with said sharpv edge lying in -a groove in said pole, said ar- -mature'having one end lying between the ends of the cores of said coils and adapted to.

vibrate. therebetween said other pole of the magnet having a hole therein and the other end of said armature ertending through said hole in saidpole a stylus holder attached tothe end of lthe armatureV extending through the hole in the pole and means for imparting 5 to said armature the vibrations to be'transmitted by said device.

In witness whereof, I have hereunto set my hand and aixed my seal, of April, 1928. l

WEHRLI D. PACK.

this 17th day l i 

